Molecular basis of inheritance : By the end of this session the student will get an idea about:
1.What is the reason behind inheritance?
2.What are the components of nucleic acids?
3.What are the characteristic features of the structure of DNA? Molecular basis of inheritance
Reason behind inheritance? : Reason behind inheritance? The reason behind inheritance is the unique genetic material present in each individual.
Types of genetic material : Types of genetic material DNA – A long polymer of deoxyribonucleotides first identified by Friedrich Meischer in 1869 within nucleus.
RNA -A long polymer of ribonucleotides rarely found as a genetic material in some viruses known as retroviruses.
Major components of Nucleic acids : Major components of Nucleic acids Nitrogenous Base
Pentose Sugar
Phosphate group
Nitrogenous bases : Nitrogenous bases Purines – Adenine(A) and Guanine(G)
Pyrimidines – Cytosine(C), Thymine(T) and Uracil(U)
Structures of Purines and Pyrimidines : Structures of Purines and Pyrimidines Reference for the figure - http://www.uq.edu.au/vdu/DNAStructure.htm
Pentose sugar : Pentose sugar DNA - Deoxyribose sugar
RNA – Ribose sugar Reference for the figure - http://www.mun.ca/biology/scarr/Ribose_sugar.html
Nucleoside formation : Nucleoside formation Nitrogenous base + pentose sugar = nucleoside
N- glycosidic bond is involved Image reference-http://www.tutorvista.com/content/chemistry/chemistry-iv/biomolecules/nucleotides-nucleosides-structure.php
Phosphate group : Phosphate group Nucleoside + phosphate = Nucleotide
Phosphoester linkage is involved Image reference - http://www.uic.edu/classes/bios/bios100/lecturesf04am/lect02.htm
Structures of different nucleotides : Structures of different nucleotides Depending on the number of phosphate groups attached to the nucleosides the naming of nucleotides is done as
Adenosine 5'–monophosphate (AMP)
Adenosine 5'–diphosphate (ADP)
Adenosine 5'–triphosphate (ATP)
Adenosine Monophosphate : Adenosine Monophosphate Image reference - http://www.traderscity.com/board/products-1/offers-to-sell-and-export-1/sell-5-adenosine-monophosphate-
Adenosine Diphosphate : Adenosine Diphosphate Image reference - http://www.shodor.org/succeed-1.0/programs/compchem97/atp/
Adenosine triphosphate : Adenosine triphosphate Image reference - http://guweb2.gonzaga.edu/faculty/cronk/biochem/A-index.cfm?definition=ATP
Formation of a dinucleotide : Formation of a dinucleotide 3'-5' phospho- diester linkage
Formation of a polynucleotide : Formation of a polynucleotide When a number of nucleotides are joined together with the help of 3'-5' phosphodiester linkages.
When bases A, T, G, C, G, T, A, C are present in a sequence the polynucleotide chain is represented as 5' ATGCGTAC 3'.
Structure of DNA : Structure of DNA Double helical model of DNA was proposed by James Watson and Francis Crick in 1953.
X–ray diffraction data produced by Maurice Wilkins and Rosalind Franklin was utilized by them.
Length of DNA which is determined by the number of base pairs is a characteristic of a particular species.
Characteristic features of the double helical structure of DNA : Characteristic features of the double helical structure of DNA Two polynucleotide chains coiled around like a spiral staircase.
Precise pairing between the nitrogenous bases.
A=T
G≡C
Slide 18 : Image reference - http://en.wikipedia.org/wiki/DNA
3.Polynucleotide chains are antiparallel in polarity. : 3.Polynucleotide chains are antiparallel in polarity. Image reference - http://www.pinkmonkey.com/studyguides/subjects/biology-edited/chap8/b0808202.asp 4.Distance between the chains is 20A0 and between the two base pairs is 3.4A0.
Characteristic features of the double helical structure of DNA : Characteristic features of the double helical structure of DNA 5. The two strands are complementary to each other
6. The plane of one base pair stacks over the other in a double helix.
Slide 21 : Thank you